Today I’m working on a WCF project that use a library in wich a method return a System.Windows.Rect.
Trying to add System.Windows to the project reference, the System.Windows references doesn’t appear on the list.
To fix the problem I found many people that use System.Windows located on Silverlight directory.
To avoid this trick I found that Rect and Size structure are included in WindowsBase.
So add WindowsBase to the project reference and the structures Rect and Size are in the same namespace System.Windows.